In Matthew 21, the Pharisees challenged Jesus, asking by whose authority He was teaching. In turn, He challenged the heart from which they were asking the question. God has always required man to teach by His authority, so Jesus received their question. Authority was required for those things taught under the Old Covenant and the same is true under the New Covenant. We can establish authority the same way the early church did: through approved examples, direct statements and inescapable conclusions.